Process for separation of mineral oil



May 30, 1933. l M, H. TUTTLE 1,912,349

PROCESS Fon SEPARATION 0F MINERAL OIL Filed Dec. 22, .1932

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FRACHON B NAPmnemc INVENTOR MMM# M 2 ATTORNEYS Patented May 30, 1933UNITED -STATES PATENT oF-FlcE MALCOLM H. TUTTI-IE, F NEW BUCHELLE, NEWYORK PROCESS FOB SEPARATION 0F MINERAL OIL I/ Application tiled December22, 1838. Serial No. 648.883.

This invention relates to a recess for the separation of mineral oilinto ractions which are `respectively more parainic 1n composition andcharacteristics and more n aphthenic in composition and, characteristicsthan-is the original oil and which ,may have 1 of being oils from theAppalachian lield; and

oils containing a relatively lower roportion of paraiiinic constituentsand t erefore a relatively higher proportion o f naihthenic constituentsare commonly calle naphthenic or Aasphaltic base oils, an example ofsuch oils being oils obtained from Gulf Coastal or Mexican fields; andoils containing an intermediate proportion of paraiiinic' constituentsand also containing naphthenic constituents are commonly called mixedbase oils, an example of such oils being oils from the Mid-Continentfields. Paraiiinic oils having a given viscosity have a lower specificgravity, a higher ash test, a smaller change of viscosity with changesin temperature and a higher ratio of hydrocarbon to carbon than donaphthenic oils of the lsame viscosity. Parailinic oils are moresuitable and more desirable as lubricants, particularly under conditionsinvolving .high temperatures and im extensive changes of temperature,than are oils in which paraiiinic constituents are present in relativelylower proportion 'and naphthenic constituents are present in relativelyhigh proportion. The characteristics of Mid-Continent or mixed base oilsare intermediate the characterictics of parilin base and asphalt baseoils.

Naphthenic oils are preferable to parafinic oils for some uses, such asinsulating oils for electrical apparatus and lubrication of REISSUEDchains and of gearing not subjected to low temperatures.

An object of this invention is to a recess whereby mineral oils may id yand economically separated into fractions which are respectively moreparainic and more naphthenlc in composition and in characteristics thanis the original oil, the separation being eifected regardless of whetherthe oil has previously been subjected to acid treatment or dewaxingtreatment or both, and without chemical reaction and without formationof sludge, to the end that solvents employed to effect such separationmay be used indefinitely and lossesV minises" mized. A specific objectof this invention is to provi e a method whereby oils obtained frommixed base ipetroleum may be separated into fractions o which at leastone is a lubricating oil stock having viscosity-gravity characteristicsand viscosity-temperature characteristics similar to or equal to orbetter than such characteristics of oil stocks having 'similar viscosityand Vobtained by usual distillation from crude oils from the Pennslvania field, a further object being the prouction' from decidedlynaphthenlc or asphaltic oil of an oil fraction of which thecharacteristics are at least substantially more parainic than thecharacteristics y of the ori 'nal oil.

o assist in understandin the e'ects and results of the practice of thismvention, reference may be made to certain values commonl employed toindicate the character of oil Thus the relation of viscosity to specificgravity is indicated by the viscosity-gravity constant determined `inaccordance with the following equation:

a ('-0.240.22 log (V.35.5)

where a=viscositygravity constant V'=Saybolt viscosity at 210 F.G=specific gravity at F.

Continent lubricatin oils have a viscositygravity constant fa ingbetween approximately .827 and .867; and na hthenic or ashalt 4baselubricating oils rom the Gulf ast and California have a viscosity-gravitconstant falling between approximately .86% and .S8-7. However, specificoils from one eld will have a viscosity-gravity constant falling withinthe range above iven for Aanother field. Moreover, the relation oftemperature to viscosit is measured b a viscosity index in whichennsylvania oi s have a value of 90 to 100 and oils of lower viscositare less paralnic and the oils of big er viscosit index are moreparalinic.

It as heretofore been proposed to treat oil with sulphuric acid for theremoval of ashalt and unstable unsaturated hydrocarns, but suchtreatment involves chemical A reaction and production of sludge fromwhich the recovery of asphalt is diilicult and uneconomical, and loss ofparailinic constituents carried down with the slud e; and the treatedoil retains marked napht enic characterisg5 tics.

It has been proposed heretofore to divide mineral oil containingnaphthenic and parafiinic-fractions into fractions more parailinic andmore na hthenic than the original oil b an extracting t e oil withnitro-aromatic so vents, which may-be termed naphthenic solvents in thatthey have greater solvent power for naphthenic constituents than forparafinic constituents, the mixture separating by gravity into an upperlayer comprising the more parainicl fraction and some ofthe solvent anda lower layer comprising the more naphthenic fraction dissolved in amajorl proportion of the solvent. ,Such treatment of mixed base oilshaving a high or intermediate asphalt content, and articularly suchtreatment of the residue o such oils, by the use of selective solventsheretofore roposedl has proven impractieable or has fai ed. The a parentcause is that the solvents proposed w en used in roportions determined beconomical consi erations a ear to be m'iscible with residual oils ofhig or intermedi-ate content of naphthenic constituents or asphalt,

with the resu t that the necessary separation into layers does notoccur. It ap ears that the nitro-aromatic solvents form with the asphaltor with the liquid naphthenie constituents, or with both a mixturehaving extensive solvent power for parainic constituents. Cresylic acidhas selective solubility for na hthenic constituents, but when used insu cient roportion to take a substantial proportion o naphthenicconstituents into solution, in an eifort to divide oil into naphthenicand arailinic fractions -by extraction, it has a su antial solvent powerfor parainic constituents.

I have found that mineral oil containing c parainic and naphthenicconstituents can be indexv separated into fractions respectively moreparaliinic. and more naphthenic than the original oil by subjectingthe'oil to contact with cresy'lic acid in the presence of a solventwhich has greater solvent power for parafflnic constituents than for nahthenic constituents, the treatment prefera ly being applied under suchconditions that the solvents employed are mutually miscible to only alimited extent. It ap ears that under such conditions, the normaselectivity of cresylic acid for naphthenic constituents is increased orits solvent power for arailnic constituents is decreased, particu arlywhen the solvent of parailnic constituents has limited solubility forand in the cresylic acid; and it appears also that the selectivity ofthe solvent for paraflnic constituents is increased or its solvent powerfor naphthenic constituents is decreased in the presence of cresylicacid. When the oil is contacted with cresylic acid in the presence ofAsuch a parainic solvent, se arationoccurs prom tly and readily.

accordance with invention, therefore, mineral oils are se arated intofractions respectively 'more para ic and more naphthenic than the or loil by extracting the oil with cresylic acid in an operation in which atleast some art of the contacting of the oil with cresylic acid occurs inthe presence of a solvent having greater solvent power for arailinicconstituents. than for naphthemc constituents. In the presence' of suchsolvent, the tenden of the cresylic acid, when present in sufficientproportion to effect substantial extraction or solution of thenaphthenic constituents, to ltake into solution` a substantialproportion of the 'paranic constituents, is minimized; `and there isproduced from a mixed base or naphtlienic oil a fraction havingcharacteristics similar to or equal to or better than the characteristiof a similar fraction obtained from paran base oil, or there is produceda fraction having characteristics at least markedly more parallinic thanthe orinal oil. Thus, the extraction of the oil wi cresylic acid in thepresence of a paranic solvent produces results heretoforeV unobtainableby the use of cresylic acid alone.

Commercial cresylic acid comprises orthocresol, metacresol,paracresol,phenol and xylenol and a reference herein to cresylic acid is intendedas a reference to such acid or to those components thereof or tomixtures of an two or more of those components. Such su ances canreadily be removed from'the oil by distillation at temperatures which donot tend to decompose the oil or the s ubstances.

Paranic solvents suitable for use in the practice of this inventioninclude ethane, propane, butane, pentane, natural soline and lightnaphtha, such light na ht a preierably being preliminarily treat with asol- 131.

vent, such as cresylic acid, having a selective solvent ower fornaphthenic constituents of oil. uch parailinic solvents have a limitedsolubility in and for cresylic acid and a greater solvent power forparainic constituents of oil than for cresylic acid and they may beremoved from the cresylic acid and from the oil for re-use bydistillation which does not involve the use of temperatures that woulddecompose the oil or the cresylic acid.

In the practice of this invention, the oil to be divided into fractionsis, at least at one point in the treatment thereof, contactedsivmultaneously with cresylic acid and a paraffinic solvent and suchcontacting may be effected in a batch operation, or in a continuousoperation in which there is preferably maintained a counter-flow ofsolvents while the oil is introducedv to such counter-flow at anintermediate point thereof and the nephthenic fraction is taken oil at apoint on the same side of the oint of introduction of the oil as thepoint o introduction of the paraffinic solvent and the naphthenicfraction is taken ol at a point on the opposite side of the point ofintroduction of the oil.

The solution of naphthenic constituents is heavier than the solution ofparaflinic constituents and in the separating operation the solution ofparaiiinic constituents forms ultimately an upper layer and the solutionof naphthenic constituents forms ultimately a lower layer. In continuousextraction, the se aration occurs in the counter-flow system. T esolution of the paraiiinic fraction will comprise paraiinic constituentsand nephthenic constituents in a ratio substantially greater than theratio of paraliinic constituents to naphthenic constituents in theoriginal oil and it will contain the major portion of the parailinicsolvent and some of the naphthenic solvent. The solution of naphthenieconstituents will include naphthenic constituents and paranicconstituents in a ratio greater than the ratio of naphthenicconstituents to parainic constituents in the original oil and willcontain the major ortion of the naphthenic solvent and some o theparaffinic solvent. The separation of parainic constituents fromnaphthenic constituents cannot be made completein a commercialoperation, but the extracting treatment produces fractions respectivelyricher in paraffinic constituents and naphthenic constituents than isthe ori al oil.

While the oil and solvents are in contact and prior to the separationinto layers above mentioned, the desired dissolving of the constituentsof the oil in the solvent or solvents may be effected by heat oragitation or both. Prior to the separation it is referable that thetemperature should be su ciently high to promote the solvent action ofthe solvents upon the constituents of the oil, but during the separationit is desirable that the tem- 'aration, but the tem perature should besuch as will promote such separation. Low temperatures promote sepratureshould not be so low as to effect solldication of any of the solvents.Moreover, in the treatment of waxcontaining oil the mixture of solventand oil should at some time before separation possess a temperature atwhich the wax is all in liquid state, but the separation may be madethereafter at a tem erature at which a part of the wax is solidi ed. Thepresence of the paraflinic solvent permits the wax present toprecipitate in particles separate from each other and from the oil,giving a mixture Which is fluid and in which the oil is free and readyto be acted upon. Thus the oil may be mixed at a temperature above themelting point of the oil, with a portion of either of the solvents thathas not been cooled or has been warmed; and after the mixture is cooledit may be introduced to the action of counterflowing solvents which areat a temperature which promotes separation.

in the practice of this invention, the lighter is the paraflinicsolvent, the greater is the specific gravity difference between thesolution of parainic fraction and the solution of naphthenic fraction,and the greater is the tendency for separation of the solutions tooccur; and the extraction operations will be conducted under suchconditions of temperature and pressure, consistent with the foregoing,that the solvents employed are in liquid phase.

ln the practice of this invention, a batch extraction step or acontinuous extraction step may be repeated as often as may be necessaryto impart to the resulting products the paratiinic and na htheniccharacteristics respectively desire for those fractions, or a continuousextraction step may be extended for a similar reason.

Thus, a feature of this invention is that the oil to be treated, whichmay be a distillate or a residue and may or may not have previously beenrefined or dewaxed, may be subjected simultaneously to contact withcresylic acid and a parallinic solvent.

A further feature of this invention is that cresylic acid alone may becaused to be capable of eiecting division in fractions respectively moreparailinic and more naphthenic an oil which would not otherwise separateinto two lavers when treated with cresylic acid alone. In accordancewith this feature of this invention the oil is first contacted withcresylic acid alone. The solution of oil constituents in cresylic acidis then extracted with a paraiiinic solvent as above set forth, the oilconstituents thus being simultaneously contacted wth both parafiinic andnaphthenic solvents. The parali'inic solvent and oil constituents insolution therein is then separated from the naphthenic solvent whichcontains naphthenc constituents in solution, and freed lli) ofparailinic solvent. The parainic constituents so obtained, and suchnaphthenic solvent and constituents as are contained therein, are thenintroduced to the oil ilowin to contact with the cresylic acid. The parainic oil constituents so added to the oil to be treated render that oilmixture capable of being divided by cresylic acid alone into'a parainicfraction and a solution of oil constituents in cresylic acid, whichfraction and solution separate readily into two layers. The upper la erof this separation is freed of cresylic aci and constitutes the desiredparaliinic fraction. Apparently the increasing of the concentration ofparaiiinic constituents in the original oil renders it separable by useof cresylic acid alone when it would not otherwise be separable by thatsolvent alone.

The naphthenic and paralinic solvents may be used in widely varyingproportions, the proportions found eifective in practice being one ,tothree parts by weight of naphthenic solvent and one toV three parts byweight of parainic solvent to each part of oil to be treated. In view ofthe wide variations in the properties of oils from different sources,the most economical proportions which produce fraction of desiredcharacter should be determined by test of the .oil to be treated.

Moreover, it is contemplated that in the practice of this invention theeli'ectiveness of cresylic acid or components thereof as naphthenicsolvents may be increased b mixing therewitha suitable proportion osolvents which have a selective solvent power and definite selectivityfor naphthenic constituents and a limited solvent power for mineral oilconstituents, and dissolve preferentially asphalts and thoseconstituents ofthe oil which are of higher molecular wei ht. Examplesofsuch solvents are sulphur dloxide, furfural, pyridine, and aniline,and inasmuch as the preferentially dissolve asphalte and constituents ofhigher molecular weight but have a limited solvent power for mineraloil, they do not have that tendency to be miscible in all proportionswith mixed base oil of high asphalt content, which tendency is possessedby dinitro-aromatic solvents.

Fig. 1 is a ilow sheet indicating the steps in the direct treatment ofoil in accordance with this invention; and

Fig. 2 is a How sheet indicating the steps in the modified procedureabove mentioned.

While the invention may be carried out by the treatment of separatebatches of oil, there are indicated in Fig. 1 the steps wherebycontinuous treatment of mixed base oils may be effected. The oil to betreated which may be either a distillate or a residue, is contacted withcresylic acid or with one or more of its components at a temperaturewhich causes the mixture to separate into layers. In the procedureillustrated, the untreated oil is continuously introduced into acontacting chamber operation preferably at an intermediate level andcresylic acid or one or more of its components is introduced into thatchamber at a suitable rate at an upper level thereof and from a similarlevel there is withdrawn paralinic fraction A while from a lower levelthere is withdrawn naphthenic fraction A which is passed into a secondcontacting operation, preferably at an upper level thereof, into whichpropane is introduced at a suitable rate, preferabl at a lower levelthereof, while there is wit drawn therefrom naphthenic fraction B andparainic fraction B which is continuously returned to the Erstcontacting operation, preferably at a lower level thereof. Parailinicfraction A is treated for the removal of propane as by the reduction ofthe pressure upon the fraction or by the application of heat or by bothof such steps. e propane is passed to propane storage while the residueof parailinic raction A is subjected to heat to effect distillationtherefrom of the cresylic acid which is passed to cresylic acid storaThe residue of the paraflinic fraction constitutes the desiredparailinic oil. The contacting ste to which is introduced naphthenicfraction and ropane, is so conducted as to effect counterow with theresult that the propane removes paranic constituents from naphthenicfraction A and carries them back to the main contacting operation, thusprovidin in the main contacting operation a counterow of parailinic andnaphthenic solvents, to a mid oint of which the oil is introduced. Napthenic fraction B is treated for the vaporization of propane as byreduction of pressure or application of heat or both of such steps, anthe propane is passed to propane storage while the residual mixture issubjected to distillation for the removal of cres lic acid, the residueof na hthenic fraction constitutin the desire naphthenic oil. Contactingc ambers employed are preferably packed to promote agitation andcontacting and they may be separate as indicated in the drawing or oinedtogether.

fer-ring to Fig. 2 of the drawing, the oil to be treatd 'is firstcontacted with cresylic acid; and t e cresylic acid containing oilconstituents in solution is then passed into contact with pro ane orother paralinic solvent which e ects a washing of the heavy fraction ofthe first contacting step. The resulting solution of paraiinicconstltuents and of small quantities of naphthenic constituents andcresylic acid in the paranic solvent separates readily from the solutionof aramnic solvent and then added to the oil li owing to the originalcontacting apithenic constituents in cresylic acid.

` amnic fraction step for immediate contact with cresylic acid alone.The treatment with cresylic acid then leaves a substantial paranicfraction undissolved and that parainic fraction forms an upper la er andis removed and is freed from cresyllc acid and constitutes the desiredparallinic oil. The naphthenic fraction, after treatment with thearaiinic solvent and removal of the para ic solution, as above stated,is treated for removal of solvents and constitutes the desirednaphthenic fraction.

The pressures and temperatures necessary in order that solvents whichare in vapor phase at normal temperature may be maintainedin liquidphase during use may be determined by reference to existing pressure andtemperature tables.

In the practice of this invention, the arroduced is more para ic thanthe origina oil and the naphthenic fraction produced is more naphthenicthan the original oil, and those two fractions are respectively moreparanic and more naphthenic than any fractions obtained by the use ofcresylic acid alone.

The araiiinic fraction may be subjected to any esired treatments such asacid treatment, clay treatment and dewaxing for the purpose of providingfinished lubricants, it being desirable in some cases to treat theparaiinic oil with a caustic soda solution, e. g. 5%, for the removal oftraces of cresylic acid before such further treatment. Herein theexpression naphthenic constituents includes asphaits and mixtures ofasphalte and naph- 'iiiieuic oils.

its a specific example of procedure in accsrdance with this invention, aresidue obtained from Mid-Continent petroleum and. having an A. P. I.gravity of 21.7, a Saybolt `Clniversal viscosity of 148 seconds at 210F. and a viscosity-gravity constant of 0.845, was treated in continuouscounter-flow contacting chambers at a temperature of 24 F. using twopounds of commercial cresylic acid and two ounds of propane per pound oforiginal oil, and the resulting products had, after removal of thesolvent, the following characteristics:

Naph- Unlisted on I ou thenlc oil Bpecle gravltygl'-.-.... m ma l'oViscosity S.U. at 210 l 148.0000 9&0000 460. 000 Viscosity-gravityconstant 0. 846 0. wl 0. 941 Yield volume 70. 8 2B. 2

of the naphthenic fraction is considerabl greater than that of theoriginal oil an greater than the viscosit -gravity constant of suchmarkedly napht enic or asphaltic base lubricating oils as oils obtainedfrom the Gulf. Cpast and California.

Th"procedure wherein paraiiinic and naphthenic solvents aresimultaneously employed and the advantages thereof are more at lengthset out in my co-pending application, Serial No. 623,483, filed July 20,1932.

It is intended that distillates and residue, refined or unrefined, maybetreated in accordance with this invention, this invention being ofspecial importance in the treatin of lubricating oils for theimprovement o the characteristics thereof. It is to be understood thatthis invention is not to be limited by any theory of operation expressedor by any example given and that it includes all modifications andvariations falling within the appended claims.

I claim:

1. In the art of refining'mineral oii comprising naphthenic and parainicconstituents, the step com rising extract the oil, in the presence o anadded liq having greater solvent power for paraiiinic constituents ofthe oil than for naphthenic constituents thereof, with cresyllc acid,the said paratiinic solvent and the cresylic acid being adapted to forma two liquid phase solvent system.

2. In the art of refining mineral oil comprising naphtnenic andparailinic constituents, the step comprising extracting the oil, in thepresence of an added liquid having greater solvent power for paranicconstituents of the oil than for naphthenic constituents thereof, withone of the group of substances consisting of orthocresoi. metacresol.

paracresol, phenol, xylenol, and a mixture of two or more thereof. thesaid paradinic solvent being adapted to form separate layers with any ofthe said group of substances.

3. In the art of refining mineral oil cornprising naphthenic andparailinic constituents, the step comprising extracting the oil, in thepresence of an added hydrocarbon solvent therefor having a boiling rangesubstantially below the boiling point of the oil, with cresylic acid,the said hydrocarbon solvent and the cresylic acid being adapted to forma two-layer solvent system.

4. In the art of refining mineral oil comprising naphthenic andparaiinic constituents, the step comprising extracting the oil, in thepresence of an added hydrocarbon solvent therefor having a boiling rangesubstantially below the .boiling point of the oil, with one of the groupof substances consisting of orthocresol, metacresol, paracresol, phenol.xylenol, and a mixture of two or more thereof, the said hydrocarbonsolvent being adapted to form a two-layer solvent liu lli

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system with any of the said group of substances.

5. In the art of refining mineral oil comprisin naphthenic and parainicconstituents, t e step compris' extracting the oil in the presence of ana ded hydrocarbon o the group consisting of ethane, propane, butane,pentane, natural gasoline, low endpoint naphtha, and a mixture of two ormore thereof, with cresylic acid, said added hydrocarbons and cresylicacid being adapted to form a two-layer solvent system.

6. In the art of refining mineral oil comprisingA naphthenic andparaiinic constituents, t e step comprising extracting the oil, in thepresence o f an added hydrocarbon of the group consisting of ethane,propane, butane, pentane, natural gasoline, low end oint naphtha, and amixture of two or more t ereof, with one of the group of substancesconsisting of orthocresol, metacresol, paracresol, phenol, xylenol, anda mixture of two or more thereof, said added hydrocarbon being adaptedto form a two-layer solvent system with each of orthocresol, metacresol,paracresol, phenol, xylenol or a mixture of two or more t ereof.

7. In the art of refining mineral oil comprising. naphthenic andparaiinic constituents, the step comprising extractin the oil, in thepresence of a petroleum nap tha previously extracted with a solventhaving greater solvent power for naphthenic than or paraiiinichydrocarbons, with one of the group of substances consisting oforthocresol, metacresol, paracresol, phenol, xylenol, and a mixture oftwo or more thereof.I and adapted to form a two-layer solvent systemwith the said extracted petroleum na htha.

8. In the art of refining mineral oi cornprising naphthenic andparailinic constituents, the'step comprising extracting the oil, in thepresence of liquid paraiiinhydrocarbons having a boiling range lowerthan the iling point of the oil, with cresylic acid, the said liquidparain hydro-carbone and cresylic acid being adapted to form a twolayersolvent system when contacted with each other.

9. In the art of refining mineral oil comprislngl naphthenic andparainic constituents, t e stepjcomprising contacting the oil withcresylic acid, and contacting the solution of oil constituents incresylic acid with a solvent having greater solvent power for parafiinicthan for naphthenic constituents of the oil, the said cresylic acid andparaiiin solvent being ada ted to form a two-layer solvent system w encontacted with 4each other.

10. In the art or refining mineral oil comprisin naphthenic andparaiiinic constituents, t e step comprising contacting the oil withcresylic acid, and contacting the oil not dissolved thereby and thesolution thereby formed with a solvent having greater solvent power forparaiinic than for naphthenic constituents of the oil, said cres licacid and paraiiin solvent being adapte to form a two-layer solventsystem when contacted with each other.

11. In the art of refining mineral oil comprisin naphthenic andparaiinic constituents, t e step com rising contacting the oil withcresylic aci contacting the solution of oil constituents in eres licacid with a solvent having greater so vent power for paraiinic than fornaphthenic constituents of the oil, and passing the solvent and oildissolved thereln into the first-mentioned contacting step, saidcresylic acid and parailin solvent being -ada ted to form a two-layersolvent system w en contacted with each other.

12. In a process of 'producing lubricating oil, the steps comprisingextractm a residue of Mid-Continent petroleum wit cresylic acid in thepresence of a solvent having greater solvent power forparaiiinic thanfor naphthenic constituents of the oil, and separating said solvent andcresylic acid from the resulting fractions, said cres lic acid andparaffin solvent being adapte to form a two-layer solvent system whencontacted with each other.

13. In a process of producing lubricating oil, the step comprisingextracting the residue of a Mid-Continent petroleum with cresylic acidin the presence of an added parainic solvent to produce fractions of the10 oil respectively richer in paraiiinic and naphthenic constituents ofthe oil, said cresvlic acid and paraiin solvent being adapted to form atwo-layer solvent system when contacted with each other.

14. In the art of refining mineral oil comprising naphthenic andparaflinic constituents, the steps comprising contacting the oil with asolvent having greater solvent power for paraiiinic than for naphthenicconstituents of the oil, and contacting the resulting solution of oilconstituents with cresylic acid, said cresylic acid and parain solventbeing adapted to form a two-layer solvent system when contacted witheach other.

15. In the art of refining mineral oil comprising naphthenic andparaiiinic constituents, the step comprising contacting the oil withcres'ylic acid, contacting the solution of oil constituents in cresylic`acid with a solvent having greater solvent power for paraiiinic than fornaphthenic constituents of the oil, separating the solvent andsubstances in solution therein from the remainder of the solution of oilconstituents in cresylic acid, removing the solvent from the substancesin solution therein, and returning said substances to the oil passing tothe iirst-mentioned contacting step, said cresylic acid and paraiiinsolvent being adapted to form a two-layer solvent system when contactedwith each other.

16. In the art of refining mineral oil, the step comprising extractinthe oil with a mixture of cresylic acid an sulphur dioxide in thepresence of a solvent havin greater solvent power for parafinic than ornephthenic constituents of the oil, the said mixture of cresylic acidand sulphur dioxide, when contacted with the said paraiinic solvent,being adapted to form a two-layer solvent system.

In testimony whereof, I have signed my name to this s ecification.

ALCOLM H. TUTTLE.

CERTIFICATE OF CORRECTION.

Patent No. 1,912, 349.

May 30, 1933.

MALCOLM H. TUTTLE.

lt is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page l,line 34, for "hydrocarbon" read "hydrcgen"; and line 36. for "suitable"read "stable"; page 6, line 61, claim 10, for "or" read "of"; and thatthe said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 25th day of July, A. D. 1933.

(Seal) M. J. Moore.

Acting Commissioner of Patents.

two-layer solvent system when contacted with each other.

16. In the art of refining mineral oil, the step comprising extractinthe oil with a mixture of cresylic acid an sulphur dioxide in thepresence of a solvent havin greater solvent power for parafinic than ornephthenic constituents of the oil, the said mixture of cresylic acidand sulphur dioxide, when contacted with the said paraiinic solvent,being adapted to form a two-layer solvent system.

In testimony whereof, I have signed my name to this s ecification.

ALCOLM H. TUTTLE.

CERTIFICATE OF CORRECTION.

Patent No. 1,912, 349.

May 30, 1933.

MALCOLM H. TUTTLE.

lt is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page l,line 34, for "hydrocarbon" read "hydrcgen"; and line 36. for "suitable"read "stable"; page 6, line 61, claim 10, for "or" read "of"; and thatthe said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 25th day of July, A. D. 1933.

(Seal) M. J. Moore.

Acting Commissioner of Patents.

